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Paris, November 29, 2005

Alain Aspect, physicist, CNRS 2005 Gold Medal

The CNRS 2005 Gold Medal has been awarded to the physicist Alain Aspect, senior researcher at CNRS (Laboratoire Charles Fabry de l'Institut d'Optique d'Orsay – Institut d'Optique/CNRS/Université Paris Sud 11), professor at the Ecole Polytechnique, and member of the French Academy of Sciences, for his research in the field of quantum optics and atomic physics. A talented experimenter, Alain Aspect has been interested all through his career in situations in which the predictions of quantum mechanics are far from being intuitive. As a teacher of repute, he has also been heavily involved in the public understanding of science and in discussion with industry.

Alain Aspect was born in 1947 in Agen, in the French department of Lot et Garonne. He studied at the Ecole normale supérieure (ENS) in Cachan and at the Université d'Orsay, passed the 'agrégation' (France's highest teaching diploma) in 1969 and defended his master's thesis at Orsay. He then did his National service, teaching for 3 years at the ENS in Yaoundé (Cameroon).

He was a lecturer at the ENS in Cachan from 1974 to 1985, and did research into pairs of entangled photons at the Institut d'Optique in Orsay. By showing that Bell's inequalities were violated, he settled the argument between Bohr and Einstein as to whether it is possible to complete the description of physical reality given by quantum mechanics (see information sheet 1). This work also enabled him, together with Philippe Grangier, to develop the first “single photon source”, emitting separate photons at identifiable moments. The quantum properties of single photons and of entangled particles are currently used in research into secure data transmission (quantum cryptography) and into quantum information processing (quantum processors).

From 1985 to 1992, he was assistant director of the Chair of atomic and molecular physics at the Collège de France, and took part in research by Claude Cohen-Tannoudji's group at the Laboratoire Kastler-Brossel (ENS Paris/CNRS/Université Paris VI) into the laser cooling of atoms. The methods they developed made it possible to substantially slow down atoms, and to reach temperatures lower than one microkelvin, i.e. less than a millionth of a degree above absolute zero. The use of ultra-cold atoms improves the accuracy of the atomic clocks which define the second, the universal unit of time (see information sheet 2).

Appointed senior researcher at CNRS in 1992, Alain Aspect founded, at the Institut d'Optique at Orsay, the atomic optics group which he still leads, and whose first work was on atomic mirrors. Since 1997, the group has mainly been concerned with studying Bose-Einstein condensates of ultra-cold atomic gases, as well as atom lasers, especially with a view to using them in atomic interferometers. These interferometers may allow accurate measurements of gravitation to be made, which would be useful both for subsurface exploration and to test general relativity, or could be used as a basis for new inertial navigation systems (see information sheet 3).By its groundbreaking research into metastable helium, the Orsay atomic optics group has also opened up new avenues in quantum atomic optics.

Alain Aspect has always combined research with teaching. At the Ecole Polytechnique, he is responsible for the course on lasers and quantum optics. He also teaches at the ENS at Cachan and in rue d'Ulm.

Although he is involved in fundamental research, Alain Aspect is a staunch believer in opening up doors between upstream research and applied research. He is highly valued as a partner by many in French industry who work in the field of optics. “Scientists who make fundamental discoveries are not necessarily the best people to think up applications for them”, he is fond of saying.“On the other hand, it is by publicizing their discoveries that they can give themselves a chance of stimulating the imagination of those who may come up with major applications. For instance, after one of the inventors of the laser, Arthur Schawlow, stated in the 1960s that the laser was a solution looking for problems to solve, industry was able to find countless applications for the laser, from bar-code scanners to optical fiber communications.”

Alain Aspect also spares no effort when it comes to the public understanding of science, whether by giving talks or by making contributions to books aimed at a non-specialized public, such as “Demain la Physique” (“Physics Tomorrow”), Odile Jacob, 2004 (chapter 5).